about JD using a pot for a position sensor on the valve? I've long suspected them of being behind the technology curve, but they can't be using a pot, can they? How do they deal with wear issues and what happens to the calibration when the resistance values change as temps the pot are subjected to change? I think you're confused.

As far as sensing the position of the steering, I am not all that sure that is desirable in every case either. As an example, take my spraying experiences last year. I seeded with a Concord and no auto-guide on the tractor. As you might imagine, with no markers, long fields and one that was a mile wide; by the time I got to the other side of the field, my rows were all over the place. When it came time to spray, I put an EZ-Steer on my no-power steering 3 wheeled Coupe. When I tried to spray just using the light-bar, I'd find myself cranking the wheel to climb out of the furrow and either run atop the ridge or cross it at a very shallow angle. As I'd come up out of the furrow, the front end would take off as it encountered less resistance. Try as I might I was hard pressed to stay within 16 inches of the line when using the steering wheel. When I put the EZ-Steer on, 4 inches was about as bad as I ever saw it get off line. In that particular case, you couldn't care less about where the steering wheel was pointing the sprayer. It had to point the wheel farther than would have been necessary on flat ground, in order to climb out of the furrow. It needed to point the wheel and then watch to see that the antenna came to the proper position, and then react in time to avoid over-correcting. I don't see where sensing position of any part of the mechanical steering mechanism would cause anything but trouble. The key there was to watch what's happening and then react to it. I'd think a tractor on a side-hill or side draft situation would be in a similar situation. The steering has to point somewhere off from the desired direction. A position sensor for the steering valve would only confuse the situation, IMHO.